Non-woven cigarette filter rod



Nov. 11, 1969 B R, PR|E ET AL NON-WOVEN CIGARETTE FILTER ROD 2 Sheets-Shes??I l Original Filed May 15, 1962 NOV. 1l, 1969 B, R, PRlCE ET AL 3,477,445

NoN-WOVEN CIGARETTE FILTER ROD Original Filed May 15, 1962 2 sheets-sheet 2 www |.Ill/ r rl 'l l`. QNiHII PN\ Nm e ww United States Patent O 3,477,445 NON-WOVEN CIGARETTE FILTER ROD Billy Ray Price, Pensacola, Fla., Richard Ernest St. Pierre, Charlotte, N.C.. and Neil E. Lloyd, Rock Hill, S.C.. assignors to Celanese Corporation, a corporation of Delaware Original application May 15, 1962, Ser. No. 194,778, now Patent No. 3,232,268, dated Feb. 1, 1966. Divided and this application Oct. 12, 1965, Ser. No. 508,409

Int. Cl. A24f 7/04, 13/02; B01d 27/00 U.S. Cl. 131--267 1 Claim ABSTRACT OF THE DISCLOSURE A non-woven cigarette filter rod having its peripheral surface free of wrinkles or dimples comprising a mass of synthetic continuous filaments wandering randomly throughout the structure in a multiplicity of directions and including numerous irregular crimp, bends and entanglements, said synthetic filaments having a lubricant applied thereto substantially immediately after formation.

This application is a division of U.S. application Ser. No. 194,778, filed May 15, 1962 now Patent No.

This invention relates to cigarette filters made of nonwoven filamentary materials, as well as to processes of and apparatus for making and treating such filters and materials.

Most cigarette filters which are presently available on the market are composed of small rods made from tows or bundles of synthetic filaments. In each filter, the component filaments extend substantially longitudinally of the cigarette, although at any given point the filaments gen- 'erally deviate from the longitudinal direction, as by being crimped. In the production of cigarette filters from such filaments, the filament producer rst forms a high denier tow of the filaments, then crimps the tow, and finally packages the same in bales or cans for shipment to the filter manufacturer. The latter, in preparing for the actual filter forming operation, must open the tow to separate the individual filaments thereof so as to deregister their crimps, in order to ensure that there will be no channels in the ultimate filters through which smoke can pass freely. The tow opening procedure is time-consuming and expensive, requiring both special apparatus and super- `visory labor, and often is not 100% efficient and leads to the production of filters having a less than maximum possible filtering power.

It has recently been proposed to avoid these drawbacks by providing a non-woven filamentary material having the form of a fiat web of randomly entangled and intersecting continuous filaments as the raw material for making the filter rods. This proposal was designed to eliminate the need for a crimping operation at the filament production plant and thus also the need for a tow opening operation at the filter and cigarette production plant. To this end, a multiplicity of synthetic filaments are extruded from a plurality of adjacent orifices or jets toward a moving belt or like take-up surface, the filaments being subjected to the action of one or more transverse streams of compressed air at a level between the jets and the takeup belt, so that the filaments are whipped about and randomly entangled with one another and are then deposited on the take-up belt in the form of the desired fiat web having a thickness of about 0.1 to 5.0 cm. and a width of about l to 75 cm.

While this procedure has proved to be advantageous in a number of respects, it has nevertheless been found to be Aattended by a number of serious problems. One of these is that the peripheral surfaces of the ultimate paperice wrapped filter plugs are frequently disfigured by a number of wrinkles or dimples. In the cigarette trade, the matter of esthetic appearance of the product is of great importance, and it is thus absolutely essential that each cigarette be unmarked, firm and of uniform diameter over its entire length. Cigarettes with wrinkled and dimpled surfaces at the filter end cannot be tolerated since they are unsightly and not attractive for the ultimate' consumers. Still further, it has been found that where such wrinkles and dimples are present, there is always a considerable weight variation over the length of the filter, while at the same time the pressure drop and filtering efficiency of the filter are appreciably reduced, which to a certain extent nullifies the value of the filter to the smoker.

The object of the present invention is the provision of cigarette filters which are free of wrinkles and dimples and have substantially greater uniformity of diameter and Weight, better filtering eliiciency and enhanced pressure drop characteristics than any known cigarette filters presently on the market.

Broadly speaking, the objectives of the present invention are achieved by the provision, at the web-forming apparatus, of a treating device in which a suitable lubricant or finish composition is applied to the web, preferably after the same has been somewhat compacted into the form of a roving-like rope, substantially immediately after its formation but prior to the baling or packaging thereof for storage `and/or shipment. In accordance with a preferred aspect of the present invention, the lubricant or finish applied to the web-material is mineral oil. Other finishes may also be used, e.g. silicone oils and alkyl esters of dibasic acids, as well as some vegetable oils and animal oils, but in any such case only if the finish is substantially free of all odor and taste. The finish is preferably applied to the extent of about 0.1% to about 2% by weight of the starting web material based on the dry weight of the latter.

The means employed for applying the finish to the filamentary material preferably comprises a self-contained unit housing a Wick roll arrangement in which a metal drum or roll rotating while partially immersed in a supply of mineral oil or other finish is in surface contact with a felt-covered wick or transfer roll which in turn is in rolling surface contact with one of a pair of feed rolls between which the said roving-like rope is passed. Such a unit also incl-udes means providing a relatively loing path of tensionfree travel for the lubricated or finished filamentary materials, s0 as to ensure that the applied treating agent can penetrate the material and reach substantially all portions thereof.

Alternatively, the lubricant or finish applicator unit may comprise means for spraying the liquid treating agent against the filamentary material. In such a case, of course, means must be provided for exhausting the unused treating agent from the atmosphere within the unit for recycling and reuse.

The foregoing and other objects, characteristics and advantages of the present invention will be more fully understood from the following detailed description thereof when read in conjunction wtih the accompanying drawings in which:

FIG. l is a schematic illustration of the webforming and treating apparatus according to the present invention;

FIG. 2 is a partly sectional elevational view of a preferred form of the lubricant applicator unit of the apparatus shown in FIG. l; and

FIG. 3 is a schematic illustration of a filter rod forming apparatus in which the lubricated filamentary material is processed |by the cigarette manufacturer.

Referring now more particularly to FIG. l, it will be seen that the apparatus for forming the filamentary material of which the ultimate cigarette filters are to be produced comprises in essence a cabinet provided with a hot air intake duct 11 and a vapor exhaust duct 12. Rotatably journaled within the cabinet are two spaced drums or shafts 13 and 1-4 around which is trained an endless belt 15 preferably made of wire mesh screen or like highly porous material. Arranged above the upper reach of the belt 15, in the region of the drum 13, is a spinnerette or jet 16 provided with a multiplicity of narrow extrusion orifices (not shown) and connected by means of a conduit 17 to a source of filament-forming dope, e.g. a solution of filament-forming `materials in a volatile solvent, under pressure. Arranged at opposite sides of the extrusion jet or series of jets 1-6, and at a level intermediate the latter and the belt 15, are two preferably inclined nozzles 18 and 19 which are oriented to direct streams of an inert Huid, such as compressed air, at the filaments F descending from the jet 16 toward the upper take-up surface of the belt 15.

In operation of this part of the apparatus, the filamentforming material in liquid phase, e.g. in solution, is extruded through the orifices in the jet 16 in the form of substantially parallel continuous filaments which are withdrawn from the extrusion area at a linear speed considerably slower than the linear speed at which the filament-forming material is extruded through the orifices, so that the weight of the resulting structure per unit length is considerably greater than if the filaments were to be withdrawn at the same linear speed at which they are extruded. Since the filaments are fairly slack, therefore, the streams of air cause the filaments to be whipped about and entangled with one another so as to Wander randomly throughout the structure. Also, in view of the fact, that the 'belt 15 is driven in the direction indicated by the arrows in FIG. 1, the entangled filament structure, upon reaching the upper surface of the belt, will be moved away from the region of the jet in the form of a matted web of predetermined width and thickness, as will be more fully explained presently. The exact rate of withdrawal will depend upon the number of orifices, the speed of extrusion and the desired denier of the structure, i.e. the desired weight in grams of 9,000 meters of the filamentary web structure. For filters for cigarettes of conventional size, e.g., about mm. in circumference, the denier of the whole material generally ranges from about 40,000 to 500,000 and preferably from about 55,000 to 100,000. The denier of the individual filaments generally ranges from about 0.5 to 25 and preferably is less than about 10. It is an advantageous feature of this arrangement that kfilaments as small as 3 denier and even less than 2 denier, if desired, can readily be produced.

'Ihe number of filaments, i.e. the number of extrusion orifices in the jet 16, may be as much as 3,000 or more although preferably it is less than about 1,800; increasing the number of filaments under a given set of spinning conditions permits the same total denier to be produced at a higher withdrawal speed. The withdrawal ratio, i.e. the ratio of the linear extrusion speed to web withdrawal speed, preferably is at least about 25, although it may be as low as about 10 or 15. Lower withdrawal ratios will reduce the effective filtration surface and/ or the randomness of the filament arrangement, which randomness contributes to the absence of channeling and to high filtration efficiency. The selected ratio will, of course, be correlated with the number of filaments and their denier to produce a web W of predetermined total denier, t-he number of filaments and their individual average denier will vary inversely, i.e. their product will be a constant which, when multiplied by the withdrawal ratio, will equal the total denier.

The width an/or the thickness of the web material may vary widely. IIn making cigarette filters, the material may be extruded under conditions giving a structure about 5 to 50 mm. or more in thickness, in which event the structure will be quite narrow, generally below 300 mm. and possibly as little as about 25 mm. Alternatively, the structure 4 may be as much as 500 mm. or more in width, in which event it will usually be only 1 or 2 mm. in thickness. Where desired, the Width may be positively controlled by providing a pair of lateral guides or bufiiles (not shown) adjacent the opposite sides of the upper reach of the belt l5. The apparent density of the material as measured with a substantially uncompressed sample is generally less than 1 pound per cubic foot.

The filaments in the web W, as already indicated, are entangled with one another and wander randomly through the web structure in a multiplicity of directions. They are characterized by irregular crimpsand bends. Inasmuch as the agitation of the filaments takes place as they are being extruded and while they are still somewhat plastic, they fuse or coalesce with one another randomly at their points of intersection, thereby providing body to the web structure which affords firmness to the resulting filters produced therefrom and eliminates the need for the subsequent steps of addition of plasticizer and curing which are customary with tow filters. The compressed air or other fluid also serves to regulate the removal of solvent from the freshly formed filaments, due to the fact that as the air expands it cools and thus prevents too rapid a removal of solvent from the filaments surfaces. As is well known, an excessively rapid removal of the solvent would have the tendency to produce on each filament a hard shell resistant to outward diffusion of the solvent from the inside.

It is preferred that, in the production of the web W, the filaments be extruded under extremely high pressures. Desirably the extrusion pressure should exceed 600 p.s.i.g., which can be attained by employing small orifices, e.g. round orifices about .O40 mm. or less in diameter, with linear rates of extrusion of 700 or more meters per minute. Under such conditions, the solvent appears to fiash ofi and produces filaments having surface characteristics different from those generally resulting from dry spinning a solution through round orifices. Specifically, in cross section they are irregular and have many lobes and deep pits, fold, indentations, striations and/or knots. They have a rough crenulated surface which resembles the bark of a tree. As a result of the striations and the knots there is more surface for a given weight of filament. The pits and irregularities permit filters formed from the web W (in a manner still to be described) to achieve a greatly increased entrapment of smoke particles, and the irregularities also produce a locking action which resists relative displacement of the filaments so that a stronger, more firm filter plug may be produced. In addition, the extreme agitation of the filaments produces small neps or coils of one or more filaments which further contribute to the ultimate attainment of a high filtration efiiciency. Although the filaments F are shown in FIG. 1 as being extruded vertically downwardly, they may be extruded downwardly and at an acute angle to the plane of the support o1' belt 15 onto which they are deposited.

In lieu of the single jet 16 shown in FIG. 1, of course, the cabinet may be equipped with a plurality of multiorificed jets in side by side relationship, and means may also be provided for reciprocating the extrusion jet or jets and/or the air nozzles across the expanse of the belt 15. Since these refinements do not constitute a part of the present invention, however, they are not explicitly illustrated in the drawings, nor will they be more fully described herein.

Examples of filament-forming materials are organic derivatives of cellulose such as ethers and/ or esters thereof, e.g. ethyl cellulose, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate formate, cellulose acetate propionate, cellulose acetate butyrate, etc., which esters may be ripened so as to modify their solubility charatceristics or may be unripened, i.e. containing fewer than about 0.29 free hydroxyl groups per anhydroglucose unit, such as cellulose triacetate. While other filament forming materials such as polyamdes, eg.

nylon 6 or 66, linear polyesters such as polyethylene terephthalate,` acrylonitrile polymers and copolymers, olefinie polymers such as polyethylene, polypropylene, polyvinyl chloride, polyvinyl acetate, polyvinyl chloride-vinyl actate, polyvinylidene chloride, and the like, can be employed, organic acid esters of cellulosesuch as cellulose acetate, arepreferred and these are advantageously extruded as a solution into a heated evaporative atmosphere. Referring further to FIG. 1, it 4will be seen that the formed web W taken up by the belt is moved toward an exit slot provided in an end wall 21 of the cabinet 10. During this time interval, substantially all of the residual solvent contained in the filaments, e.g. acetone in the case of cellulose acetate filaments, evaporates and is removed from the interior atmosphere of the cabinet 10 via the duct 12, leaving the web W effectively dry and with thevarious filaments thereof bonded to one another at their points of inter-section. Thereafter, upon issuing from the cabinet 10, the web W is passed through a forming nozzle or like structure 22 in which it is reduced in width into the form of a roving-like rope R the width of which may range from about 25 to about 100 mm.

Ordinarily, when the rope R is baled or packaged at this point of the process in the usual can or like container and by means of a conventional baling press, for example as indicated schematically at 2 3 in FIG. 1, the rope is subjected to externally applied compression forces which tend to result in the formation of nicks and creases in the folded filamentary material at a great number of places generally coinciding with the location of the folds. In the normal case, of course, this compression continues for some time, as long as the bale is in storage and awaiting use of the filamentary material in the production of cigarette filters. Such nicks and creases appear in the filamentary material even after relatively short periods o f compression and become more pronounced as the storage .time increases. Tests have shown that it is at the locations of these nicks Vand creases that the subsequently formed filter rods and plugs are defective, having a reduced hardness and a number of wrinkles and dimples in the surrounding paper wrappers, and that such filter rods are generally also defective due to the occurrence, in any given "unit length of filter rod, of substantial variations in the outerdiameter of the rod as well as in its filtration efficiency and pressure drop characteristics.

By way of explanation of the occurrence of such wrm- `kles and dimples, it appears that they are due to the presence of a number of longitudinally spaced spots in the lilamentary material at which the latter is somewhat thicker than normal. Itis easily understandable that these thicker parts are constituted by the -,folds in the web or rope which tmay become set to a certain extent, in the form of the `and more, the drag it exerts on the filmentary material increases. If, therefore, a web or roving-like rope having `relatively thick spots therein is fed lthrough the tongue,

the deposited acetate crust causes a greater dragl to be "exerted on the thicker portions of the material `than on the thinner ones. Thus, as each of the said thicker portions, .e. the folds, of the web or rope reaches the tongue where the crust build-up has occurred, it tends to become trapped so that the section 'of the web or rope prior to each fold or crease is subjected to a considerable pull and necked, resulting in a plurality of thin spots in the rope. When the latteris subsequently shaped to filter 'rod form and wrapped with paper, the rod as well as the I6 paper will be disiigured by one or more wrinkles or dimples.

It is to eliminate these drawbacks and disadvantages that the rope R formed from the web material W is passed, prior to the `baling thereof, through a lubricant applicator unit 24 where a suitable lubricant is applied to it in a manner to be more fully explained presently.

In accordance with a preferred aspect of the present invention, the lubricant comprises any suitable commercially available grade of mineral oil, for example light mineral oils marketed under the designations Bayol 50 (viscosity: 50 Saybolt seconds at 100 F. and 33.4 Saybolt seconds at 210 F.; specific gravity: 0.8268 at 60 F. and 0.8221 at 77 F.) and Bayol F (viscosity: 53 Saybolt Aseconds at 100 F. and 34 Saybolt seconds at 210 F.; specific gravity: 0.18286 at 60 F. and 0.8237 at 77 F.). The lubricant is preferably applied to the filamentary material in amounts ranging from about 0.1% to about 2% by weight of the dry filamentary material, and most preferably between about 0.15 and 0.80% by weight of said material.

As previously indicated, the treatment of the filamentary material in accordance with the principles of the present invention effectively eliminates the occurrence of wrinkles and dimples on the ultimately formed filter rods. The application of the lubricant, e.g. mineral oil, to the ilamentary material prior to the baling thereof enhances interfiber lubricity and thus reduces both the setting of the folds and the friction at thetongue. Tests have shown that the filamentary material as produced and lubricated in accordance with the present invention does not become nicked and creased even after extremely prolonged periods of compression in a bale.

Referring now to FIG. 2, according to a preferred aspect of the present invention, the lubricant applicator unit 24 comprises a base 25 to the top of which is affixed a central horizontal mounting plate 269 which supports a variable-speed drive mechanism 27 of any desired construction. The mechanism 27, which may be started and stopped by means of a switch 27a, is operatively connected via -a chain or drive belt 28 to the shaft 29 of a highly polished oiler roll 30` having a diameter of about mm. and a length of about 65 mm., the shaft 29 `the lubricant in the reservoir 31 is maintained with the aid of an overflow pipe 33. The oiler roll 30 is in frictional rolling surface contact `with a felt-covered oil transfer roll v-34 having a diameter of about 70 mm. and a length of about 75 mm., the shaft 34a of this roll being rotatably `supported at its opposite ends in a bearing bracket assembly 35 carried by an arm 35a adapted Vto be revolved about the axis of the shaft 29. The oil transfer roll 34 may thus be-moved between its solid-line 'and brokenline positions shown in FIG. 2.

Also rotatably journaled in a suitable bearing structure Iatop the base 25 are two substantially vertically superposed rolls 36 and 37 made of metal or any other suitable "hard, material and each having a diameter of about 75 mm. and a length of about 250 mm., the upper roll 36 being smooth-surfaced and positioned to be in rolling surface contact with the lower roll 37 and with the felt- `covered Vroll 34 when the latter is in its solid-line position. The lower roll 37 is preferably tinted longitudinally and is positively driven by any suitable drive mechanism '7(not' shown) which may be actuated through a switch 37a.` Positioned at the opposite sides of the base 25 and adjacent the ends of the various rolls are two guard plates 38 (only one is shown).

Supported by the base 25 in the center thereof is a substantially Ytrough-shaped structure or I-box 39 one 7 end of which is located at a point just belofw the discharge side of the fiuted roll 37, and the other end of which is located at a point adjacent the opposite side of the base 25. At its said other end, the I-box 39 carries a guide member 40 which is disposed below the intake side of a pair of feed rolls 41 which are arranged in the same horizontal plane and are rotatably journaled in a suitable bearing structure on the base 25. As at the other end, the base is provided with a pair of guard plates 42 (only one is shown).

In operation, as the oiler roll 30 is rotated by the drive means 27-28, it transfers a quantity of mineral oil or like lubricant from the reservoir 31 to the feltcovered roll 34, which in turn transfers the lubricant onto the smooth-surfaced roll 36. Consequently, with the roving-like rope R being drawn through the nip of the rolls 36 and 37, of which the lower and fluted roll 37 is positively driven while the upper roll 36 rotates due to its frictional contact with the lower roll, the lubricant is applied to the rope at that portion of the surface thereof which is in Contact with the roll 36. By virtue of the nature of the original filamentary web, the oil begins substantially immediately to spread and diffuse into the interior parts of the rope. Moreover, the arrangement of the two sets of rolls 36-37 and 41-41 and the manner of feeding the rope through the unit 24 are such that the rope travels without any externally applied tension, except for its own weight, and thus in as completely slack a condition as possible. As a result, the portion of the rope R disposed between the lubricating rolls 36-37 and the feed rolls 40 hangs downwardly, as indicated at R', from its points of contact With respective roll pairs and along the curved bottom 39a of the I-box 39. This increases the length of the path of travel of each given segment of the lubricated rope through the Iunit 24 and permits the oil applied to the rope to seep further into and penetrate through the entire rope before the latter leaves the lubrieating unit.

The lubricated rope, upon leaving the applicator unit 24, may then be packaged or baled in any suitable shipping container 23 in a manner well known to the art. However, as has already been stated hereinbefore, even when the baled iilamentary material remains under compression for a substantial period of time, it remains free of nicks and creases, which eliminates the formation of wrinkles and dimples in the paper Wrapping of the ultimately formed filter rods.

As clearly shown in FIG. 3, at the cigarette manufacturing plant the rope R is drawn out of the bale or package 23 and fed, for example, with the aid of a pair of feed rolls 43 to the inlet trumpet or tongue 44 of a filter rod forming machine 45. In the trumpet 44 the rope R is still further condensed and compacted, as indicated at R", so that -its cross section approximates that of a cigarette. The so compacted rope or rod R" then enters a paper wrapping unit 46 of the apparatus 4S together with a strip of paper P and an endless belt 47, the paper being wrapped about the rope R" and glued in the unit 46 in a conventional manner. The paper-wrapped filter rod 48 issuing from the unit 46 is then cut by a knife 49 into filter plugs 50 of predetermined length. These filter plugs, which are then ready to be combined with tobacco into filter tip cigarettes in a conventional manner, are completely free of wrinkles and dimples. This result is achieved by virtue of thefact that, in addition to the prior elimination of creases, the build-up of acetate dust at the tongue 44, as well as at the apparatus 46, is greatly reduced, thus effectively eliminating any excessive drag on the rope R (and R) as it passes through the tongue 44 and into the apparatus 46 and the concurrent differential stretching hereinbefore mentioned.

It will be readily understood that the application of lubricant to the filamentary material may be effected in other'ways than by means of a multiple transfer roll systern as shown in FIG. 2. Merely by way of example, the

rope R of filamentary material may be passed through a spray chamber in which the lubricant is blown at and over the material by means of one or more atomizer nozzles. Alternatively, the material may be lrun across a constantly wetted wick or like element maintained in contact with a quantity of the lubricant. It will also be clear that the lubricant may be applied to the originally formed web W prior the formation thereof into the roving-like rope R. In either of these alternative systems, i.e. spray or wick, there must be provided means for metering the lubricant, including devices for controlling the pressure and fiow conditions thereof, as well as (in the case of a spray system) means for exhausting any vapor-laden air to special lubricant recovery apparatus. In particular in a transfer or wick roll system as shown in FIG. 2, however, it is possible in accordance with the present invention to control the amount of lubricant applied within very precise limits. This may be achieved by regulating the speed of rotation of the polished oiler roll 30, which can be done by suitably setting the drive mechanism 27, since the rate of transfer of lubricant to the felt-covered roll 34 is a direct function of the speed of rotation of the oiler roll 30.

The lubrication of the filamentary material also leads to a number of other noteworthy results, apart from the aforesaid elimination `of wrinkles and dimples in the finished filters. In substantially eliminating the problem of tongue waxing, it Ileads to greater productivity as Well as to greater economy of production of cigarette filters. This will be readily understood when it is considered that the encrustation deposit must be removed periodically, which necessitates shutting down the filter rod mak-ing apparatus at specified intervals to permit the tongue assembly to be cleaned. Moreover, the filter rods R and filters 50 produced from the so lubricated flamentary material are possessed of greatly enhanced pressure drop characteristics, while variations in weight and diameter per unit length of filter rod are substantially reduced. Also, especially when mineral oil is employed as the lubricant, the resultant filters are found to be almost completely free of all odors and taste, a result which it has been substantially impossible to achieve heretofore with filters employing other additives or finishes.

The following example will serve to illustrate the prin ciples of the invention more clearly.

EXAMPLE l A 26.8% by weight solution of cellulose acetate, having an acetyl value of 55 in acetone is extruded through a jet having 304 circular holes each 0.032 mm. in diameter. The linear extrusion speed is about 2000 meters per minute. The pressure at the extrusion jet 16 is about 300 p.s.i.g., while the pressure at the source of thedope is 500 p.s.i.g. The temperature of the solution is C. The upper reach of the take-up belt 15 in the cabinet 10 is positioned 275 mm. below the jet 16 and advances ata speed of 50 meters per minute. Compressed air at '.20 p.s.i.g. and 25 C. is directed from the nozzles 18 and 19 against the extrusion filaments F at an angle of about 45 to the vertical, the nozzles being so arranged that the air blasts impinge on the filaments at a distance" of about 15 cm. below the jet. 'Ihe resulting web W of randomly tangled filaments is about 0.3 cm. thick andhas a total denier of about 80,000. Upon leaving the cabinet 10, the web V-W -is formed into a roving-like rope R having a diameter of about 1.5 cm. The rope R is then passed through the lubricant applicator unit 24 shown in FIG. 2 where about 0.5% by weight of mineral oil (based on the dry Weight of the filamentary rope R) is applied to the surface of the rope from the reservoir 31 through the intermediary of the rolls 30, 34 and 36. After passing through the applicator unit freely suspended between the sets of rolls 36-37 and 41-41, the lubricated rope is baled and shipped to a cigarette making plant. There it is fed into a conventional filter making apparatus and converted into paper-wrapped filter plugs 17 mm. long, about 25 mm. in circumference, and weighing about 0.155 gram each. When tested, such filter plugs are found to be completely free of wrinkles and dimples. By way of comparison, filter plugs of the same dimensions were made from two batches of the same type of filamentary web material which were not lubricated prior to baling, and one of which was kept in baled form under compression for a longer period than the other. About 21% of the plugs made from the material which was compressed for the shorter period of time were found to be defective due to wrinkling and dimpling, while about 64% of the plugs made from the material baled for the longer period of time were found to be so defective. At the same time, the plugs made from the lubricated iilamentary material are found to have greater hardness, higher pressure drop and improved filtration efliciency, as well as more uniform circumference and weight characteristics, than the plugs made from the other batches of unlubricated filamentar material.

It is to be understood that the foregoing detailed description is given merely by Way of illustration, and that many variations may be made in the invention without any departure from the spirit thereof.

Having described our invention, what we desire cure by Letters Patent is:

1. A cylindrical filter rod adapted to be cut into individual filter plugs for cigarettes, each of the plugs being to secharacterized by having all of its peripheral surfaces rela tively free of dimples or wrinkles, each being of uniform diameter and weight and presenting good efficiency without significant pressure drop, said cylindrical rod being formed by :depositing a web of libres selected from the group consisting of cellulose esters, poleolefins, polyamids, acrylonitriles and polyesters, the fibers of the web being randomly arranged and presenting irregular crimps, bends and entanglements, the said fibres further being coalesced to one another at radom points of contact, the said fibre web being formed into a rope which is impregnated with a material consisting essentially of a mineral oil in an amount of .l to 2% by weight of the dry mass of filaments, and said web being formed onto a rope and then finally shaped into cylindrical rod form.

References Cited UNITED STATES PATENTS 2,828,752 4/ 1958 Jackson 131--267 2,900,988 8/ 1959 Crawford et al 131-267 3,119,396 1/ 1964 Tanquary 131--269 X 3,148,101 9/1964 Allman et al.

MELVIN D. REIN, Primary Examiner U.S. C1. X.R. ISI- 268; 161--170 

